Process of utilizing furnace-flue dust.



UNITED STATES PATENT orrion.

PROCESS OF UTILIZING FURNACE-FLUE DUST.

Specification of Letters Patent.

Patented Nov. '7, 1905.

Application filed March 26, 1905. Serial 1:10. 251,99

To all whom, it may concern:

Be it known that I, SAMUEL B. SHELDON, a resident of Buffalo, in thecounty of Erie and State of New York, have invented a new and usefulImprovement in Processes of Utilizing Furnace-Flue Dust; and I do herebydeclare the following to be a full, clear, and exact descriptionthereof.

My invention relates to a process of producing coke for metallurgicalpurposes, and more especially to such a process which will also enablethe utilization of blast-furnace List In the reduction of iron ore inblast-furnaces a large amount of dust is produced and passes out of thefurnace. The quantity of such dust Varies with different characters ofore and also with different conditions of working the furnace and is avery decided waste unless the same can be utilized. This dust consistsof fine coke or other carbon, lime, and fine ore or partially-reducedore. The quantity of ore varies by weight of the total amount of dustand represents a considerable percentage of the value of the ore beingreduced. This dust is collected in suitable dust-catchers and must thenbe dis posed of, and if thrown away the labor necessary to remove it isan additional expense. Heretofore attempts have been made to utilizethis flue-dust, one being by wetting the same and again charging intothe blast-furnace. Opinions differ as to the efficiency of this method;but the weight of opinion is that either this dust at once passes out ofthe furnace or else inducesconditions which tend to increase theproduction of flue-dust by the furnace. It has also been proposed tosinter the flue-dust in suitable rotary kilns. This requires apparatuswhich is expensive to maintain and also entails a considerable amount oflabor. Furthermore, the sintering process in the kiln resultspractically in the oxidation of the carbon contained in the flue-dust,so that this ingredient is practically lost.

My process has for its object to utilize such flue-dust and in a mannerwhich is eco nomical and which does not affect the working of theblast-furnace.

The invention consists, generally stated, in mixing the flue-dust withthe coal which is used for coke, so that in the coking process thecarbon of'the flue-dust will be incorporated with the coke and the orecontained therein will be either wholly or partially reduced to ametallic state. I have discovered that a percentage of flue-dust can bemixed with the coking-coal without in any manner affecting the cokingprocess or impairing the quality of the coke. In fact, it seems toincrease the quality of the coke, as the metallic iron or suboxid ofiron, or both, resulting from the reduction of the ore in the dust binusthe coke all the more firmly together. There is also a considerablepercentage of lime in the flue-dust, and this fluxes with the siliciousmaterial in the coal and serves to bind the coke more firmly togetherand improves its physical structure. This coke can be then utilized forany metallurgical purpose, preferably for blast-furnace work, beingcharged in the required proportion in the ordinary manner into thefurnace and the process carried on in the usual way. The character ofthe flue-dust is so changed in the coking that .it is not again carriedout of the furnace.

My invention can be carried into effect with any existing forms ofapparatus, and as these form no part of the invention they are neitherillustrated nor described.

The blast-furnace may be of any suitable form, and the dust producedthereby will be collected in any known or desired manner. This dust willbe conveyed by any suitable means to the coking plant, and the latteralso may be of any existing or preferred construction. Here theflue-dust will be mixed with the coal in the necessary proportions inany suitable manner either by hand or machinery. The mixture will thenbe charged into the coking-oven in the usual way, and the coking processwill be carried on exactly as heretofore. Any form of coking-oven willbe employed, either beehive or, preferably, of retort or by producttype, as the latter usually are located in closer proximity to theblast-furnaces than the beehive type.

During the coking process the reducing atmosphere which is producedreduces all the iron in the flue-dust either to a metallic state or to asuboxid of iron, or both. The lime of the flue-dust fluxes with thesilicious matter in the coal, and the carbon of the fluedustis-incorporated with the coal, and thus made available for furtherproduction of iron in a blast-furnace. v

The quantity of flue-dust mixed with the coke may vary to a considerableextent. 1t may be mixed with the coal in such quantities that all theflue-dust produced by the furnace will be incorporatedwith the quantityof coke which that furnace will need in thefurther production of iron.As the quantity of flue-dust produced by furnaces varies, the proportionof the same to the coal used for coking will also vary. I have foundthat under ordinary conditions a quantity of fluedust amounting to aboutthree to five per cent. of the weight of the coal used for coking Willpractically consume all of the flue-dust produced. As this flue-dustcontains a considerable per cent. in Weight of iron ore, a considerableloss is prevented, and the metallic iron produced by the reducingprocess in the coke-oven and the fluxing action of the lime on thesilicious matter of the coal binds the structure of the coke morefirmlytogether and increases its value for blast-furnace work, this firmcoke producing less flue-dust than is produced by the use of a cokehaving a loose structure.

My process of utilizing the flue-dust does not necessitate any additionsto or changes in existing blast-furnaces or coking plants. It can bemixed with the coal Without any special apparatus whatsoever, and theamount of labor necessary to do this is very little greater than isnecessary to carry the flue-dust away to dump. It in no mannerinterferes With or mo difies the existing processes either of coking thecoal or reducing the ore, and therefore adds nothing either to the costor labor of these processes. As a consequence it provides a veryeconomical Way of disposing of the flue-dust, and at the same time allof said dust is saved, both the carbon and the ore contained therein.

What I claim is- 1. The process of utilizing blast-furnaceflue dust,which consists in mixing flue-dust and coal in substantially theproportions of flue-dust produced by a furnace and the amount of coalconsumed by said furnace, and then coking the mixture.

2[ The process of utilizing blast-furnaceflue dust, which consists inmixing the same with coal, the proportion of flue-dust being from threeto five per cent. of the Weight of the coal, and then coking themixture.

In testimony whereof I, the said SAMUEL B. SHELDON, have hereunto set myhand.

SAMUEL B. SHELDON. l/Vitnesses:

F. H. BURNETT, MARY E. CARR

